B&M Nitrous HoleShot 3800 Torque Converter, 1965-91 GM TH400, TH425 TH375B, 1965-81 GM TH350

10-inch diameter, 10.75-inch bolt circle, 3500-3800 RPM stall

PART# 20485

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Fits vehicles with GM TH400, TH425, TH375 & TH350, TH375B (Not TH350C) Automatic Transmissions


B&M Nitrous HoleShot 3800 stall for GM 1965-91 TH400, TH425, TH375 and 1968-81 TH350, TH375B (not TH350C.) The Nitrous Holeshot 3800 stall converter is an excellent choice for vehicles with engine modifications, particularly big cams that tend to reduce low end power and torque. The higher stall speed of this converter will launch the car in a higher rpm range where more torque is readily available, resulting in quicker acceleration. Nitrous Holeshot converters feature furnace brazed impeller and turbine, new precision steel alloy pump drive tube, new heavy duty needle bearings between the stator and impeller (not a thrust washer) and needle bearings between the stator and turbine. Other features include dual pattern 10.75 and 11.50-inch bolt circle, a new turbine hub, new springs and rollers in the stator and anti-balloon plates. The anti-balloon plates will allow these converters to stand up to the instant horsepower that a nitrous plate system delivers. Stall speed listings are based on engines producing 230lb. ft. of torque at 2,500 rpm. More torque at 2,500 rpm will give you more stall speed, less torque at 2,500 rpm will give you less stall speed than the stall speed ratings indicated. These are serious converters for serious performance street cars. To prevent contamination left from worn parts being circulated in your new components causing premature wear, we strongly recommend protecting your investment by adding a B&M transmission cooler with all new transmission installations. Listed converters are NOT to be used in trans-brake applications. Not for use in trans-brake applications.


  • Needle Bearing Between Stator and Turbine
  • Higher Stall Speed, Quicker Acceleration
  • Anti-balloon Plate for Added Strength
  • Furnace Brazed Impeller and Turbine
  • Fully Balanced and Pressure Tested
  • Steel Alloy Pump Drive Tube
  • B&M Quality & Durability


Additional ContentsNew needle bearings
Anti Balloon PlateYes
Anti-Balloon PlateYes
Automotive Item GradeHigh Performance
Bolt Circle Diameter (in)10.75
California Proposition 65 RequiredNo
Crank Pilot Diameter (in)1.71
Emission Code5
FlexPlate Bolt Circle10-3/4", 11-1/2"
Flexplate Change NeededNo
Furnace BrazedYes
Lockup TypeNo
Mounting StudsNo
Product TypeTorque Converters
Stall Speed3500-3800
Torque Converter SeriesNitrous Holeshot
Transmission ModelTH400, TH425, TH375, TH350
Part Number20485


This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations.

In The Box

In The Box

  • Torque Converter
  • Mounting Hardware

Tech Resources

Fits vehicles with GM TH400, TH425, TH375 & TH350, TH375B (Not TH350C) Automatic Transmissions


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